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Would it be a bad idea to rotate a lithium ion battery at a
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Would it be a bad idea to rotate a lithium ion battery at a

by zphricz on Thu Aug 22, 2019 2:23 pm

I want to make a persistence-of-vision display by attaching dotstar LEDs onto an industrial fan. I am looking at this fan here: https://www.homedepot.com/p/Commercial- ... /303061465

I'm not entirely sure what the rpm is at the moment, but some of the reviews suggest that it can get over 1,000rpm, which seems pretty fast. For the project, I want to mount a lithium ion battery to the blade somehow in order to power the LED and the onboard microcontroller. I figure I'd actually use two, mounted on opposing blades, to try to reduce vibrations as much as possible.

Spinning a lithium ion battery at over 1,000rpm sure doesn't sound like a good idea off the top of my head, but I'm curious if it would be possible at all. Assuming that safely mounting the battery to the blades wasn't a concern, is there a limit to the forces that a lithium ion battery can safely handle? I would try to mount it as close as I could to the center of rotation to reduce the forces involved as much as possible, but I'm curious if there is no way to make this work safely at all.

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Re: Would it be a bad idea to rotate a lithium ion battery a

by adafruit_support_bill on Thu Aug 22, 2019 2:57 pm

I don't know of any published specs regarding tolerance of acceleration forces. Obviously it would need to be very securely mounted.

Another option would be to mount the battery on the fan housing somewhere and use a slip-ring to get power to the rotating blades.
https://www.adafruit.com/?q=slip

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Re: Would it be a bad idea to rotate a lithium ion battery a

by zphricz on Thu Aug 22, 2019 4:43 pm

Yeah, I actually bought a slip ring from you already for this, but I haven't bought the fan yet, so I haven't tested out whether or not it will work. I might consider using that to start, if I can find a way to mount it easily onto the fan. The main problem that I have with that is that it says it's max rated at "300RPM (but you can probably go faster if you don't mind a reduced life and/or noise)."

This would be 1,000RPM or more, so it seems like it would be either a significant reduction in life, or maybe it will just break right away? Is there any information on people's attempts to use these at above 300RPM that I could use for reference?

On another note, I had asked my coworkers about this problem, and they suggested that I build a commutator with brushes (essentially building a slip ring). Perhaps if I could do that, I could make something more durable. I feel like I'd want that to be a stretch goal though, since I have no experience in that. Do you know of any high speed, durable hobby-oriented slip rings that could be used for this? Whenever I google this, I can only find industrial slip rings which seems like they'd be far too expensive for a hobby project.

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Re: Would it be a bad idea to rotate a lithium ion battery a

by adafruit_support_bill on Thu Aug 22, 2019 5:04 pm

I've done a lot of searching for slip-rings also. These are about all there is in the hobbyist price range. I have not tried them at 1000RPM. I would not expect them to self-destruct at that speed. But the wear would be accelerated (these don't have ball-bearings like the high-price industrial ones).

Some industrial fans can be wired or switched to run at various speeds. If you can find one that is capable of running slower, that would improve your odds with either the slip ring or a blade-mounted LiPo.

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Re: Would it be a bad idea to rotate a lithium ion battery a

by luciusjo on Fri Aug 23, 2019 3:33 pm

1000rpm shouldn't be a problem. I have a battery in a Motorsport application rotating at about 2000rpm, in a very high G environment. The shock/vibration doesn't seem to be a detriment.

Jim J.

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Please be positive and constructive with your questions and comments.